Spoofing in the context of secure fingerprint systems is the act of using a fake finger—typically one made of gelatin, silicone, or Play-Doh®—to gain illicit access to services protected by a biometric system. “Fake finger” refers to any non-human apparatus designed to fool the fingerprint system. “Spoofing” is the act of using a fake finger to gain illicit access. “Vitality detection” or “live finger detection” refers to the ability of a system to distinguish between live human fingers and non-living real or fake fingers.
Prior art literature states that it is easy to make molds of latent fingerprints left behind by legitimate users. While inexperienced persons may still have some difficulty creating fake fingers from latent prints, the process has definitely gotten easier and more accessible over the past few years. Therefore, the security of these systems is jeopardized, and it is becoming necessary to offer some protection against this threat in the form of “anti-spoofing” methods.
Some prior art anti-spoofing systems use methods to determine the vitality of a finger presented to a fingerprint sensor. Most of these systems are hardware-based, resulting in significantly higher costs, as well as a significantly larger sensor. These larger sensors are unacceptable for mobile devices, which typically require a very small sensor size. The prior art generally teaches, among other things, using characteristics of a finger such as finger surface resistance, temperature, pulse, and blood oximetry.
None of these prior art systems are known to work very well. In a typical system, a parameter such as surface resistance is measured by hardware, and then logic (hardware or software based) simply checks to make sure the sensed value is within an acceptable range. This can be repeated for a plurality of metrics, with all the metrics treated independently.
Prior art software-based solutions are not adaptable to swipe-type fingerprint sensors. Specifically, these systems require that successive full-size images of a finger be analyzed to merely determine whether the finger is sweating. This process takes many seconds to complete, at the user's inconvenience.